The present invention relates to multiple-input, multiple output (MIMO) communication systems, and more particularly, to a MIMO system that uses knowledge of the statistics of the communication channel to prefilter the transmit signal(s).
In recent years, there has been much interest in multiple input, multiple output (MIMO) systems for enhancing data rates in mobile communication systems. MIMO systems employ multiple antennas at the transmitter and receiver to transmit and receive information. The receiver can exploit the spatial dimensions of the signal at the receiver to achieve higher spectral efficiency and higher data rates without increasing bandwidth.
The best performance in a MIMO system is obtained when the channel response is known to the transmitter. In this case, the transmitter can use knowledge of the channel response to compute antenna weights for each antenna so as to compensate for the channel conditions between the transmitter and the receiver. The amount of channel feedback from the receiver in such systems increases with the number of antennas at the transmitter and the receiver. The channel feedback from the receiver to the transmitter consumes valuable reverse link resources. Therefore, it is desirable to reduce the amount of feedback required to be sent on the reverse link while maintaining good performance on the forward link.